The present invention relates to improvements in antifriction means for plungers, and is more particularly concerned with a new and improved antifriction roller means, especially useful for reciprocatable plungers which are subject to transverse thrust in operation.
In some reciprocatable plunger equipped apparatus, the plunger is frequently, and in some instances regularly subjected to transverse thrust which causes localized friction between the plunger perimeter and the wall surface of the housing or guide bore in which the plunger is caused to reciprocate. This friction is especially bothersome when performance testing the tool. It is to the alleviation of such friction that the present invention is directed.
An example of a typical apparatus in which the lateral or transverse friction-prone thrust of a plunger is experienced in the operation of the apparatus, is torque control mechanism for wrenches, and the like. An example is disclosed in the copending application of the present applicants, Ser. No. 713,381 filed Jun. 10, 1991, now U.S. Pat. No. 5,129,293 issued Aug. 14, 1992, and the disclosure of which is incorporated herein by reference for whatever help it may be to a thorough understanding of the disclosure herein, and to reduce to a comfortable minimum disclosure detail necessary for exemplifying a best mode representation of the present invention.
Heretofore, alleviation of lateral thrust friction in respect to the plungers of torque control mechanism for wrenches has been addressed by providing ball bearings about the perimeter of the plunger of the mechanism as disclosed in U.S. Pat. No. 3,270,594. While that arrangement provides some improvement due to the smooth surface, it still does not attain sufficient friction alleviation to attain the best test results for that class of instruments. Because of the necessary frictional engagement of the ball bearings in their races direct rubbing exists and only about 80% antifriction results are obtainable within textbook friction parameters, and which may even drop below that level if there is inadequate attention to lubrication.